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// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
use crate::{
event,
event::{
api::{Path, SocketAddress},
IntoEvent,
},
inet,
};
#[derive(Debug)]
#[non_exhaustive]
pub struct Attempt<'a> {
/// The path that the connection is currently actively using
pub active_path: Path<'a>,
/// Information about the packet triggering the migration attempt
pub packet: PacketInfo<'a>,
}
#[derive(Debug)]
pub struct AttemptBuilder<'a> {
/// The path that the connection is currently actively using
pub active_path: Path<'a>,
/// Information about the packet triggering the migration attempt
pub packet: PacketInfo<'a>,
}
impl<'a> From<AttemptBuilder<'a>> for Attempt<'a> {
#[inline]
fn from(builder: AttemptBuilder<'a>) -> Self {
Self {
active_path: builder.active_path,
packet: builder.packet,
}
}
}
#[derive(Debug)]
#[non_exhaustive]
pub struct PacketInfo<'a> {
pub remote_address: SocketAddress<'a>,
pub local_address: SocketAddress<'a>,
}
#[derive(Debug)]
pub struct PacketInfoBuilder<'a> {
pub remote_address: &'a inet::SocketAddress,
pub local_address: &'a inet::SocketAddress,
}
impl<'a> From<PacketInfoBuilder<'a>> for PacketInfo<'a> {
#[inline]
fn from(builder: PacketInfoBuilder<'a>) -> Self {
Self {
remote_address: builder.remote_address.into_event(),
local_address: builder.local_address.into_event(),
}
}
}
// TODO: Add an outcome that allows the connection to be closed/stateless reset https://github.com/aws/s2n-quic/issues/317
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
#[non_exhaustive]
pub enum Outcome {
/// Allows the path migration attempt to continue
///
/// Note that path validation will still be attempted as described in
/// [Section 8.2](https://datatracker.ietf.org/doc/html/rfc9000#section-8.2).
Allow,
/// Rejects a path migration attempt
///
/// The connection will drop the packet that attempted to migrate and not reserve any state
/// for the new path.
Deny(DenyReason),
// Additional outcomes must be handled in the path::Manager
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum DenyReason {
// The new address uses a port that is blocked
BlockedPort,
// The new address uses a port in a different scope
PortScopeChanged,
// The new address uses an IP in a different scope
IpScopeChanged,
// All connection migrations are disabled
ConnectionMigrationDisabled,
}
impl IntoEvent<event::builder::ConnectionMigrationDenied> for DenyReason {
#[inline]
fn into_event(self) -> event::builder::ConnectionMigrationDenied {
let reason = match self {
DenyReason::BlockedPort => event::builder::MigrationDenyReason::BlockedPort,
DenyReason::PortScopeChanged => event::builder::MigrationDenyReason::PortScopeChanged,
DenyReason::IpScopeChanged => event::builder::MigrationDenyReason::IpScopeChange,
DenyReason::ConnectionMigrationDisabled => {
event::builder::MigrationDenyReason::ConnectionMigrationDisabled
}
};
event::builder::ConnectionMigrationDenied { reason }
}
}
/// Validates a path migration attempt from an active path to another
pub trait Validator: 'static + Send {
/// Called on each connection migration attempt for a connection
fn on_migration_attempt(&mut self, attempt: &Attempt) -> Outcome;
}
pub mod default {
use super::*;
use crate::path::remote_port_blocked;
#[derive(Debug, Default)]
pub struct Validator;
impl super::Validator for Validator {
#[inline]
fn on_migration_attempt(&mut self, attempt: &Attempt) -> Outcome {
let active_addr = to_addr(&attempt.active_path.remote_addr);
let packet_addr = to_addr(&attempt.packet.remote_address);
// Block migrations to a port that is blocked
if remote_port_blocked(packet_addr.port()) {
return Outcome::Deny(DenyReason::BlockedPort);
}
//= https://www.rfc-editor.org/rfc/rfc9000#section-21.5.6
//# it might be possible over time to identify
//# specific UDP ports that are common targets of attacks or particular
//# patterns in datagrams that are used for attacks. Endpoints MAY
//# choose to avoid sending datagrams to these ports or not send
//# datagrams that match these patterns prior to validating the
//# destination address.
// NOTE: this may cause reachability issues if a peer or NAT use different
// port scopes for the same connection. Additional research may
// be required to determine if this countermeasure needs to be relaxed.
if PortScope::new(active_addr.port()) != PortScope::new(packet_addr.port()) {
return Outcome::Deny(DenyReason::PortScopeChanged);
}
//= https://www.rfc-editor.org/rfc/rfc9000#section-21.5.6
//# Endpoints MAY prevent connection attempts or
//# migration to a loopback address. Endpoints SHOULD NOT allow
//# connections or migration to a loopback address if the same service
//# was previously available at a different interface or if the address
//# was provided by a service at a non-loopback address.
//= https://www.rfc-editor.org/rfc/rfc9000#section-21.5.6
//# Similarly, endpoints could regard a change in address to a link-local
//# address [RFC4291] or an address in a private-use range [RFC1918] from
//# a global, unique-local [RFC4193], or non-private address as a
//# potential attempt at request forgery.
// Here, we ensure the ip scope match so peers are unable to change after
// establishing a connection
match (active_addr.unicast_scope(), packet_addr.unicast_scope()) {
(Some(a), Some(b)) if a == b => Outcome::Allow,
_ => Outcome::Deny(DenyReason::IpScopeChanged),
}
}
}
#[derive(Debug, PartialEq, Eq)]
enum PortScope {
System,
User,
Dynamic,
}
impl PortScope {
#[inline]
pub const fn new(value: u16) -> Self {
//= https://www.rfc-editor.org/rfc/rfc6335#section-6
//# o the System Ports, also known as the Well Known Ports, from 0-1023
//# (assigned by IANA)
//#
//# o the User Ports, also known as the Registered Ports, from 1024-
//# 49151 (assigned by IANA)
//#
//# o the Dynamic Ports, also known as the Private or Ephemeral Ports,
//# from 49152-65535 (never assigned)
match value {
0..=1023 => Self::System,
1024..=49151 => Self::User,
49152..=65535 => Self::Dynamic,
}
}
}
fn to_addr(addr: &SocketAddress) -> crate::inet::SocketAddress {
match addr {
SocketAddress::IpV4 { ip, port, .. } => {
crate::inet::SocketAddressV4::new(**ip, *port).into()
}
SocketAddress::IpV6 { ip, port, .. } => {
crate::inet::SocketAddressV6::new(**ip, *port).into()
}
}
}
}
pub mod disabled {
use super::*;
#[derive(Debug, Default)]
pub struct Validator;
impl super::Validator for Validator {
fn on_migration_attempt(&mut self, _attempt: &Attempt) -> Outcome {
// deny all migration attempts
Outcome::Deny(DenyReason::ConnectionMigrationDisabled)
}
}
}
#[cfg(any(test, feature = "testing"))]
pub mod allow_all {
use super::*;
#[derive(Debug, Default)]
pub struct Validator;
impl super::Validator for Validator {
fn on_migration_attempt(&mut self, _attempt: &Attempt) -> Outcome {
// allow all migration attempts
Outcome::Allow
}
}
}